Insulating glass unit transparent conductivity and low emissivity coating technology

ABSTRACT

The invention provides flash-treated transparent conductive coatings based on indium tin oxide. Some embodiments provide a multiple-pane insulating glazing unit that includes two glass panes and a between-pane space. The two glass panes respectively define two opposed external pane surfaces. At least one of the two external pane surfaces has a flash-treated transparent conductive oxide coating.

PRIORITY

This application is a continuation-in-part of U.S. Utility applicationSer. No. 14/185,287, filed on Feb. 20, 2014, which is a continuation ofU.S. Utility application Ser. No. 13/006,992, filed on Jan. 14, 2011 andnow issued as U.S. Pat. No. 8,658,262, which claims priority to U.S.Provisional Application No. 61/295,694, filed on Jan. 16, 2010.

FIELD OF THE INVENTION

The present invention relates generally to thin film coatings for glassand other substrates. More particularly, this invention relates toflash-treated transparent electrically conductive coatings based onindium tin oxide.

BACKGROUND OF THE INVENTION

A variety of transparent electrically conductive oxide (“TCO”) coatingsare known in the art. In some cases, these coatings include an indiumtin oxide (“ITO”) film. To obtain a desired balance of electricalconductivity and visible transmission, ITO-based coatings are often heattreated. Known heat treatments include furnace heating, laserirradiation, flame treatment, and flash lamp treatment. Flash lamptreatment is beneficial in that it heat treats a large area of thecoating with a single flash while the underlying substrate remainsrelatively cool.

It would be desirable to provide transparent electrically conductivecoatings based on ITO that facilitate improved properties upon flashtreatment. It would be particularly desirable to provide flash-treatedtransparent electrically conductive coatings based on ITO that providecombinations of properties improved for use on one or two exteriorsurfaces of a multiple-pane insulating glazing unit. It would also bedesirable to provide transparent electrically conductive coatingsdesigned for ultra-high-power flash treatment that producesflash-treated ITO-based coatings having an improved combination ofproperties.

It would be desirable, for example, to provide a flash-treated ITO filmthat has specific combinations of thickness, optical properties, andhigh electrical conductivity. It would also be desirable to provide aflash-treated ITO film that has pre and post flash optical bandgapsenabling good absorption, during the flash, of radiation in the range of370-400 nm. In addition, it would be desirable to provide aflash-treated ITO film having a particular morphology that results fromultra-high-power flash treatment. The resulting film preferably wouldhave surface roughness, carrier concentration, and absorption propertiesthat are particularly advantageous for use on one or both exteriorsurfaces of a multiple-pane insulating glazing unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a broken-away schematic side view of a production line inaccordance with certain embodiments of the present invention;

FIG. 2 is a broken-away schematic cross-sectional view of a substratebearing a transparent electrically conductive coating in accordance withcertain embodiments of the invention;

FIG. 3 is a broken-away schematic cross-sectional view of a substratebearing a transparent electrically conductive coating in accordance withother embodiments of the invention;

FIG. 4 is a broken-away schematic cross-sectional view of a substratebearing a transparent electrically conductive coating and atitanium-oxide containing film in accordance with still otherembodiments of the invention;

FIG. 5 is a partially broken-away schematic cross-sectional side view ofa multiple-pane insulating glazing unit that includes an exterior paneand an interior pane, the interior pane having a fourth surface carryinga flash-treated transparent electrically conductive coating inaccordance with certain embodiments of the invention;

FIG. 6 is a partially broken-away schematic cross-sectional side view ofa multiple-pane insulating glazing unit that includes an exterior paneand an interior pane, the interior pane having a fourth surface carryinga flash-treated transparent electrically conductive coating and ahydrophilic and/or photocatalytic film in accordance with otherembodiments of the invention;

FIG. 7 is a partially broken-away schematic cross-sectional side view ofa multiple-pane insulating glazing unit that includes an exterior paneand an interior pane, the exterior pane having a first surface carryinga flash-treated transparent electrically conductive coating, and theinterior pane having a fourth surface carrying another flash-treatedtransparent electrically conductive coating, in accordance with stillother embodiments of the invention;

FIG. 8 is a partially broken-away schematic cross-sectional side view ofa multiple-pane insulating glazing unit that includes an exterior paneand an interior pane, the exterior pane having a first surface carryinga hydrophilic and/or photocatalytic film, and the interior pane having afourth surface carrying a transparent electrically conductive coating,in accordance with yet embodiments of the invention; and

FIG. 9 is a partially broken-away schematic cross-sectional side view ofa multiple-pane insulating glazing unit that includes an exterior paneand an interior pane, the exterior pane having a second surface carryinga low-emissivity coating, and the interior pane having a fourth surfacecarrying a flash-treated transparent electrically conductive coating, inaccordance with further embodiments of the invention.

SUMMARY OF THE INVENTION

In some embodiments, the invention provides a multiple-pane insulatingglazing unit comprising two glass panes and a between-pane space. Thetwo glass panes respectively define two opposed external pane surfaces.A desired one of the two external pane surfaces has a flash-treatedtransparent conductive oxide coating such that a desired one of the twoglass panes is a coated glass pane. This coated glass pane is annealedglass having a surface stress of less than 3,500 psi. The coatingcomprises a flash-treated indium tin oxide film and an overcoat film onthe flash-treated indium tin oxide film. The flash-treated indium tinoxide film has a thickness of less than 1,800 Å. The flash-treatedindium tin oxide film is a sputtered film having a surface roughness ofless than 3 nm. The flash-treated indium tin oxide film has a sheetresistance of less than 15 Ω/square in combination with the coated panehaving a monolithic visible transmittance of greater than 0.82. Theflash-treated indium tin oxide film has an optical bandgap of 370 nm orshorter and is characterized by a pre-flash optical bandgap of 400 nm orlonger. The multiple-pane insulating glazing unit includes an internalpane surface bearing a low-emissivity coating that has only one filmcomprising silver. The film comprising silver contains at least 50%silver by weight. The low-emissivity coating is exposed to thebetween-pane space. In the present embodiments, the multiple-paneinsulating glazing unit has a U value of less than 0.25 together with anIGU visible transmission of greater than 75%.

Certain embodiments of the invention provide a multiple-pane insulatingglazing unit comprising two glass panes and a between-pane space. Thetwo glass panes respectively define two opposed external pane surfaces.A desired one of the two external pane surfaces has a flash-treatedtransparent conductive oxide coating such that a desired one of the twoglass panes is a coated glass pane. This coated glass pane is annealedglass having a surface stress of less than 3,500 psi. The coatingcomprises a flash-treated indium tin oxide film and an overcoat film onthe flash-treated indium tin oxide film. The flash-treated indium tinoxide film has a thickness of less than 1,800 Å. The flash-treatedindium tin oxide film is a sputtered film having a surface roughness ofless than 3 nm. The flash-treated indium tin oxide film has a sheetresistance of less than 15 Ω/square in combination with the desired panehaving a monolithic visible transmittance of greater than 0.82. Theflash-treated indium tin oxide film has an optical bandgap of 370 nm orshorter and is characterized by a pre-flash optical bandgap of 400 nm orlonger. The multiple-pane insulating glazing unit includes an internalpane surface bearing a low-emissivity coating that has only two filmscomprising silver. Each of the two films comprising silver contains atleast 50% silver by weight. The low-emissivity coating is exposed to thebetween-pane space. In the present embodiments, the multiple-paneinsulating glazing unit has a U value of less than 0.25 together with anIGU visible transmission of greater than 65%.

Some embodiments of the invention provide a multiple-pane insulatingglazing unit comprising two glass panes and a between-pane space. Thetwo glass panes respectively define two opposed external pane surfaces.A desired one of the two external pane surfaces has a flash-treatedtransparent conductive oxide coating such that a desired one of the twoglass panes is a coated glass pane. This coated glass pane is annealedglass having a surface stress of less than 3,500 psi. The coatingcomprises a flash-treated indium tin oxide film and an overcoat film onthe flash-treated indium tin oxide film. The flash-treated indium tinoxide film has a thickness of less than 1,800 Å. The flash-treatedindium tin oxide film is a sputtered film having a surface roughness ofless than 3 nm. The flash-treated indium tin oxide film has a sheetresistance of less than 15 Ω/square in combination with the coated panehaving a monolithic visible transmittance of greater than 0.82. Theflash-treated indium tin oxide film has an optical bandgap of 370 nm orshorter and is characterized by a pre-flash optical bandgap of 400 nm orlonger. The multiple-pane insulating glazing unit includes an internalpane surface bearing a low-emissivity coating that includes three filmscomprising silver. Each of the films comprising silver contains at least50% silver by weight. The low-emissivity coating is exposed to thebetween-pane space. In the present embodiments, the multiple-paneinsulating glazing unit has a U value of less than 0.25 together with anIGU visible transmission of greater than 60%.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description is to be read with reference to thedrawings, in which like elements in different drawings have likereference numerals. The drawings, which are not necessarily to scale,depict selected embodiments and are not intended to limit the scope ofthe invention. Skilled artisans will recognize that the examplesprovided herein have many useful alternatives that fall within the scopeof the invention.

The invention provides methods for producing a coated substrate. Themethods involve depositing a transparent conductive coating onto asubstrate and flash treating the coated substrate. Preferably, thecoating is deposited by sputter deposition. In other cases, the coatingis deposited by chemical vapor deposition, spray pyrolysis, sol-geldeposition, atomic layer deposition (ALD), or pulsed laser deposition.Once the coating has been deposited, it is flash treated. The presentmethod preferably uses an ultra-high-power flash treatment system. Theterms “ultra-high-power flash treatment” and “UHP flash treatment” aredefined for purposes of the present disclosure to mean flash treatmentat a peak pulse power of 15 kW/cm² or greater. It will be appreciatedthat this is higher than the peak pulse powers commonly reported forconventional flash lamp treatment.

Thus, a substrate (10 or 10′) having a surface (12 or 18) is provided.If desired, this surface (12 or 18) can be prepared by suitable washingor chemical preparation. A variety of substrate types are suitable foruse in the invention. In some cases, the substrate is a sheet-likesubstrate having opposed first and second surfaces, which can optionallybe rectangular. The substrate can be a sheet of transparent material(i.e., a transparent sheet). The substrate, however, is not required tobe transparent.

For many applications, the substrate will comprise a transparent (or atleast translucent) material, such as glass or clear plastic. Forexample, the substrate is a glass sheet (e.g., a window pane) in certainembodiments. A variety of known glass types can be used, such assoda-lime glass. In some cases, it may be desirable to use “whiteglass,” a low iron glass, etc. In certain embodiments, the substrate ispart of a window, door, skylight, or other glazing. Depending on thelevel of solar control desired, the present coating may be applied totinted glass. Thus, the coating of any embodiment disclosed herein canoptionally be provided on a sheet of tinted glass. This may provideparticularly good selectivity.

Substrates of various sizes can be used in the present invention.Commonly, large-area substrates are used. Certain embodiments involve asubstrate having a major dimension (e.g., a length or width) of at leastabout 0.5 meter, preferably at least about 1 meter, perhaps morepreferably at least about 1.5 meters (e.g., between about 2 meters andabout 4 meters), and in some cases at least about 3 meters. In someembodiments, the substrate is a jumbo glass sheet having a length and/orwidth that is between about 3 meters and about 10 meters, e.g., a glasssheet having a width of about 3.5 meters and a length of about 6.5meters. Substrates having a length and/or width of greater than about 10meters are also anticipated. In some embodiments, the substrate is acontinuous ribbon, such as a float glass ribbon emanating from a floatglass production line or a ribbon on a roll-to-roll system.

Substrates of various thicknesses can be used in the present invention.In some embodiments, the substrate (which can optionally be a glasssheet) has a thickness of 1-14 mm, such as 2-14 mm. Certain embodimentsinvolve a substrate with a thickness of between about 2.3 mm and about4.8 mm, and perhaps more preferably between about 2.5 mm and about 4.8mm. In one particular embodiment, a sheet of soda-lime glass with athickness of about 3 mm is used.

The substrate (10 or 10′) has opposed surfaces (12 and 14, or 16 and18), which preferably are major surfaces (as opposed to edge surfaces).In some cases, surface 16 is destined to be an internal surface exposedto a between-pane space of an insulating glazing unit, while surface 18is destined to be an external surface exposed to an interior of abuilding. This, however, need not be the case in all embodiments.

The coating 7 is deposited onto a surface (12 or 18) of a substrate (10or 10′), e.g., as one or more discrete layers, as one or morethicknesses of graded film, or as a combination including at least onediscrete layer and at least one thickness of graded film. Preferably,the present method involves sputtering, e.g., DC magnetron sputtering,which is a well-known deposition technique. Reference is made toChapin's U.S. Pat. No. 4,166,018, the teachings of which areincorporated herein by reference. In some cases, the coating 7 isdeposited by AC or pulsed DC sputtering from a pair of cathodes. HiPIMSand other modern sputtering methods can be used as well.

Briefly, magnetron sputtering involves transporting a substrate (10 or10′) through one or more low pressure zones (or “chambers” or “bays”) inwhich the one or more film regions that make up the coating 7 aresequentially applied. To deposit oxide film, the target(s) may be formedof an oxide itself, and the sputtering may proceed in an inert oroxidizing atmosphere. To deposit indium tin oxide, for example, aceramic indium tin oxide target can be sputtered in an inert oroxidizing atmosphere. Alternatively, oxide film can be deposited bysputtering one or more metallic targets (e.g., of metallic indium tinmaterial) in a reactive atmosphere. Tin oxide can be deposited bysputtering one or more tin targets in a reactive atmosphere containingoxygen gas. Silicon nitride can be deposited by sputtering one or moresilicon targets (which may be doped with aluminum or the like to improveconductivity) in a reactive atmosphere containing nitrogen gas. Siliconoxynitride can be deposited by sputtering one or more silicon targets(which may likewise be doped with aluminum or the like) in a reactiveatmosphere containing both oxygen and nitrogen gas. Silicon dioxide canbe deposited by sputtering one or more silicon targets (which maylikewise be doped with aluminum or the like) in a reactive atmospherecontaining oxygen gas. Titanium dioxide can be deposited by sputteringone or more titanium targets (which may be doped with tungsten or thelike) in a reactive atmosphere containing oxygen gas, or by sputteringtitanium sub-oxide targets in an inert gas, a reactive gas, or a mixtureof both. The thickness of the deposited film(s) can be controlled byvarying the speed of the substrate, by varying the power on the targets,and/or by varying the ratio of power to partial pressure of the reactivegas.

In one example, a pair of rotatable ceramic indium tin oxide targets issputtered while an uncoated glass substrate is conveyed past theactivated targets at a rate of about 36 inches per minute. The relativeweight amount of the two metals is: indium 90%, tin 10%. A power of 16kW is used, and the sputtering atmosphere is 5 mTorr with a gas flow of900 sccm argon and 10 sccm oxygen. The resulting substoichiometricindium tin oxide film has a thickness of about 1,100 Å. Directly overthis film, a silicon nitride overcoat film is applied. The siliconnitride is applied at a thickness of about 560 Å by conveying the glasssheet at about 36 inches per minute past a pair of rotary siliconaluminum targets (83% Si, 17% Al, by weight) sputtered at a power of31.2 kW in a 5 mTorr atmosphere with a gas flow 920 sccm nitrogen. Forthe as-deposited film, the visible absorption is about 8.5%, the opticalbandgap is about 430 nm, the carrier concentration is about1.5×10²⁰/cm³, and the surface roughness is about 2.7 nm.

In another example, a pair of rotatable metallic indium tin targets issputtered while an uncoated glass substrate is conveyed past theactivated targets at a rate of about 60 inches per minute. The relativeweight amount of the two metals is: indium 90%, tin 10%. A power of 16kW is used for the pair of rotary targets. The sputtering atmosphere is5 mTorr with a gas flow of 601 sccm argon and 100 sccm oxygen. Theresulting substoichiometric indium tin oxide film has a thickness ofabout 1,240 Å. Directly over this ITO film, a silicon nitride overcoatfilm is applied. The silicon nitride is applied at a thickness of about600 Å by conveying the glass sheet at about 60 inches per minutesequentially past a pair of rotary silicon aluminum targets (83% Si, 17%Al, by weight) sputtered at 38.6 kW in a 5 mTorr atmosphere with a gasflow 450 sccm argon and 451 sccm nitrogen. For the as-deposited film,the visible absorption is about 10.5%, the optical bandgap is about 420nm, the carrier concentration is about 2.5×10²⁰/cm³, and the surfaceroughness is about 2.9 nm.

The foregoing examples are merely exemplary. Many other sputterdeposition processes can be used to deposit the coating 7 onto thesubstrate (10 or 10′). Moreover, chemical vapor deposition, spraypyrolysis, sol-gel deposition, atomic layer deposition (ALD), or pulsedlaser deposition can alternatively be used.

FIG. 1 schematically depicts a production line having both a sputtercoater 400 and a flash treatment device 500. Here, the flash treatmentdevice 500 is located on the production line downstream of the coater400. The flash treatment device can alternatively be located within thecoater. Another possibility is to provide the flash treatment device 500on a processing line separate from the sputter coater 400. The flashtreatment device 500, for example, may be in a facility different fromthe coating facility. Either way, the sputtering line 400 will typicallyinclude a series of connected sputter deposition chambers through whicha path of substrate travel P extends. The path of substrate travel P canbe defined, for example, by a series of spaced-apart transport rollersTR.

The flash treatment device 500 preferably has a single row of flashlamps, although this is not strictly required. The flash lamps can be,for example, xenon flash lamps each having a diameter larger than 15 mm.The flash lamps can be spaced apart by, for example, about three incheson center across the width of the system, with the axis of the lampaligned in the direction of travel of the substrate. As one non-limitingexample, for a 96 inch width of treated glass area, 32 lamps may beused. The lamps preferably each have a length of six inches, althoughother lengths (e.g., longer lengths) can alternatively be used. Aconcentrating reflector is mounted behind each lamp, e.g., such that thelamp uniformly illuminates a 3 inch×6 inch area (or, in the case oflonger lamp lengths, larger areas can be uniformly illuminated).

As another possibility, the flash treatment device 500 can include oneor more lamps each having their axis cross-wise to the direction ofsubstrate travel. Lamps of various lengths can be used in such cases,depending upon the requirements of a given system and its intendedapplications.

The present flash treatment preferably involves a peak pulse power of 15kW/cm² or greater, e.g., in the range of 15-45 kW/cm², or even 20 kW/cm²or greater, e.g., in the range of 20-45 kW/cm². Thus, the present flashtreatment preferably is UHP flash treatment. Thus, the flash-treatedindium tin oxide film may have a morphology characterized by UHPflash-treatment at 15-45 kW/cm². Due to the rapid temperature change ofthe film, a distinctive average stress condition may result.

When the device 500 flashes, it preferably emits a pulse packet ofbetween 1 and 20 pulses. These pulses can be as long as 5 milliseconds,but preferred recipes involve 5-15 pulses, each being between 50 and 200microseconds, with an off-time in the range of 50-100 microsecondsbetween each pulse. One exemplary pulse packet is about 2 millisecondsin length (including on and off time). The pulse is powered by a chargedcapacitor bank. The energy contained in the pulse is affected by thelength of the pulse, as well as the voltage at which the capacitors havebeen charged. The voltage range preferably is between 650 V and 950 V.The total energy contained in a pulse packet is up to about 30 J/cm²,and preferably is in the range of from 18 J/cm² to 24 J/cm². The peakpower of the pulse preferably is 15 kW/cm² or greater, e.g., in therange of 15-45 kW/cm², or even 20 kW/cm² or greater, e.g., in the rangeof 20-45 kW/cm².

The system is able to flash up to approximately two such pulse packetsper second (limited by the capacitor recharging rate). A single pulsepacket is sufficient to convert the film, but there may be some overlapof pulse packets (e.g., 10%) to ensure the film is fully treated. Incertain embodiments, each pulse treats 6 inches in the direction oftravel (preferably with a 10% overlap), and the line speed is as high asabout 650 inches per minute (e.g., 5.4+5.4=10.8 inches per second).Equipment of this nature is commercially available from Ncc Nano LLC ofAustin, Tex., U.S.A.

Thus, the invention provides a method for producing flash-treated coatedglass. The method involves providing a glass substrate (10 or 10′)having opposed first (12 or 18) and second (14 or 16) surfaces. Anindium tin oxide film 20 is deposited onto the first surface (12 or 18)of the glass pane (10 or 10′). The indium tin oxide film 20, asdeposited, is a sub-oxide (i.e., its oxygen content issubstoichiometric). The deposition technique can be, for example, inaccordance with either of the two non-limiting sputter depositionexamples detailed above. Other deposition methods can alternatively beused. Preferably, the method involves sputtering a metallic indium tintarget in an oxidizing atmosphere. One such deposition technique is thesecond of the two non-limiting sputter deposition examples detailedabove. The substoichiometric indium tin oxide film (i.e., the film 20 asdeposited) has a thickness of less than 1,800 Å, a surface roughness ofless than 3 nm, an optical bandgap of 400 nm or longer, and a carrierconcentration of 5×10²⁰/cm³ or less.

Thus, the thickness of the substoichiometric indium tin oxide film(i.e., the film 20 as deposited) is less than 1,800 Å, such as between100 Å and 1,800 Å. In some cases, the thickness is less than 1,600 Å,such as between 100 Å and 1,600 Å, or even less than 1,500 Å, such asbetween 100 Å and 1,500 Å. In preferred embodiments, the thickness isbetween 1,050 Å and 1,450 Å. Any embodiment disclosed herein can providethe thickness of film 20 in this range. The thicknesses recited hereinare physical thicknesses unless otherwise specified to be opticalthicknesses.

As noted above, the substoichiometric indium tin oxide film (and thecoating 7) has a surface roughness R_(a) of less than 3 nm. In preferredembodiments, the surface roughness R_(a) is between 1.5 nm and 3 nm,such as between 2.0 nm and 3.0 nm. Surface roughness is defined in termsdeviations from the mean surface level. The surface roughness R_(a) isthe arithmetical mean surface roughness. This is the arithmetic averageof the absolute deviations from the mean surface level. The arithmeticalmean surface roughness of a coating is commonly represented by theequation: R_(a)=1/L∫₀ ^(L)|f(x)|dx. The surface roughness R_(a) can bemeasured in conventional fashion, e.g., using an Atomic Force Microscope(AFM) equipped with conventional software that gives R_(a).

In connection with the optical bandgap of the substoichiometric indiumtin oxide film, because it is 400 nm or longer (and hence in the visibleregion), the film 20 as deposited has lower transmission in the visiblerange. The optical bandgap determines the portion of the solar spectrumthat the indium tin oxide film 20 will absorb; photons with an energylevel less than that of the bandgap are not absorbed. The opticalbandgap can be determined from the optical absorption spectrum of thematerial using a Tauc Plot. This method is well known to skilledartisans. This method is well known to skilled artisans. In anyembodiment of the present disclosure, the optical bandgap of thesubstoichiometric indium tin oxide film can optionally be 410 nm orlonger, or even 420 nm or longer.

The carrier concentration of the indium tin oxide film 20 is relativelylow (5×10²⁰/cm³ or less) as deposited. Thus, the as-deposited film isnot very conductive. In certain preferred embodiments, the film 20 isdeposited so its carrier concentration is in the range of about1-2.5×10²⁰/cm³. The carrier concentration can be determined using thevan der Pauw Method, which is well known to skilled artisans.

In addition, the substoichiometric indium tin oxide film preferably isnon-porous, or at least substantially non-porous. Porosity is a measureof the volume fraction of voids (empty space or a gas or liquid phaseseparate from the film material) in a film, also called the voidfraction.

It is to be appreciated, however, that it is merely optional to providethe film 20 in non-porous or substantially non-porous form. Anotheroption is to have higher amounts of porosity. While this may decreasethe electrical conductivity of the film 20, it may also reduce its indexof refraction, which may be advantageous for certain applications.Porosity can be provided using methods well known to skilled artisans,such as increasing the pressure during sputtering.

The method further includes flash treating the substoichiometric indiumtin oxide film so as to produce a flash-treated indium tin oxide film.The flash treatment equipment and process parameters described above canoptionally be used. While an UHP technique is preferred, it is notrequired. Similarly, the equipment arrangement details discussed aboveare optional. Skilled artisans will be able to readily design and usemany other flash treatment equipment arrangements and process parametersgiven the present teaching as a guide.

The flash-treated indium tin oxide film has an optical bandgap of 370 nmor shorter, a carrier concentration of 9×10²⁰/cm³ or more, and a sheetresistance of less than 15 Ω/square in combination with providing thecoated glass substrate with a monolithic visible transmittance ofgreater than 0.82.

The flash treatment advantageously crystallizes the indium tin oxidefilm 20, improves grain size, heals intra-grain defects, oxidizes thefilm (and decreases visible absorption), optionally together withactivating dopant(s) in the film. As noted above, the carrierconcentration of the as-deposited indium tin oxide film is relativelylow. It is therefore not very conductive. And because its opticalbandgap is in the visible region, the film 20 as deposited has lowertransmission in the visible range. As a result of the flash treatment,the optical bandgap of the film 20 shifts to a higher energy/shorterwavelength. By shifting the bandgap from 400 nm or longer (pre-flash) to370 nm or shorter (post-flash), the indium tin oxide film 20 is capableof absorbing energy emitted by the flash in the 370 to 400 nm range. Themechanism that causes the bandgap to shift when the carrierconcentration increases is the Burstein Moss Effect.

The flash treatment preferably produces a carrier concentration factorof at least 5. That is, the carrier concentration of the flash-treatedindium tin oxide film preferably is at least 5 times greater than thecarrier concentration of the substoichiometric indium tin oxide film(i.e., the film 20 as deposited). In some embodiments, the carrierconcentration factor is at least 7.5. The carrier concentration of theas-deposited film can be, for example, in the range of 1-2.5×10²⁰/cm³.The flash treatment provides a great carrier concentration increase.Preferably, the carrier concentration of the flash-treated indium tinoxide film is in the range of 9-13×10²⁰/cm³.

The flash treatment lowers the sheet resistance of the indium tin oxidefilm 20. The post-flash sheet resistance is less than 30 Ω/square, suchas 5-28 Ω/square. In some cases, it is less than 15 Ω/square, less than14 Ω/square, or even less than 13 Ω/square, such as 10-13 Ω/square.Sheet resistance can be measured in standard fashion using a non-contactsheet resistance meter.

The flash treatment produces a controlled ΔA for the indium tin oxidefilm 20. The term ΔA is defined, for purposes of the present disclosure,as being the magnitude of the reduction of the visible absorption of theindium tin oxide film 20 caused by the flash treatment. As is well-knownto skilled artisans, visible absorption (expressed as a percentage)equals 100 minus T_(vis) minus R_(vis). Preferably, the ΔA is fivepercent or more, seven percent or more, or even nine percent or more.The visible absorption of the substoichiometric indium tin oxide film(i.e., the film 20 as deposited) preferably is greater than 7%, e.g., inthe range of 7.5-12%. After flash treatment, the visible absorptionpreferably is less than 5%, such as 0.5-4.5%, perhaps optimally 1-4%.

The flash treatment can optionally be preceded by a step of pre-heatingthe coated glass. In some embodiments, prior to flash treating thecoated substrate, it is heated to a temperature of greater than 50degrees C., or even greater than 75 degrees C., such as about 100-125degrees C. The optional preheating can be conducted using an electricfurnace, a natural gas furnace, or infrared lamps. As just one example,a pre-heating system can optionally be positioned between the coater 400and the flash-treatment device 500 in the embodiment of FIG. 1.

The flash treatment is advantageous in that it, while it heats thecoating 7 to an extremely high temperature, the heating period isincredibly short, so the glass substrate (10 or 10′) experiencesrelatively little heat gain. For example, the opposite surface of theglass pane is maintained at a temperature of 150 degrees C. or lower(preferably lower than 125 degrees C.) during the flash treatment. Thisis desirable for several reasons. First, the annealed state of a coatedglass substrate can be maintained even after flash treatment; the glasscan thus remain cut-able. Second, the glass is not subjected to thetypes of deformations (e.g., roller wave distortion) that can occur inconventional furnace tempering. Third, the time, energy, and costsavings are considerable.

The flash-treated indium tin oxide film has a low sodium concentration.Preferably, the sodium concentration is less than 100 ppm, less than 10ppm, or even less than 1 ppm. During heat treatment, sodium can migratefrom substrate materials like soda-lime glass into an overlying coating.(In preferred embodiments, the or each glass substrate is soda-limeglass.) It is desirable to keep the ITO film 20 as sodium-free aspossible. When a significant amount of sodium is present in an ITO film,its long term stability and performance may be negatively impacted.Since flash treatment subjects the glass substrate to far less heat thanfurnace tempering and other conventional heat treatments, the presentflash method is beneficial in terms of avoiding sodium poisoning. Thesodium concentration can be measured using secondary ion massspectroscopy, which is a technique well known in the present field.

The thickness of the indium tin oxide film 20 after flash treatment isless than 1,800 Å, such as between 100 Å and 1,800 Å. In some cases, thethickness of the flash-treated indium tin oxide film is less than 1,600Å (but greater than 100 Å), or even less than 1,500 Å (but greater than100 Å), and yet its sheet resistance is less than 13 Ω/square. Thethickness can be, for example, between 1,050 Å and 1,800 Å, such asbetween 1,050 Å and 1,450 Å. In certain preferred embodiments, thethickness is in this range and the monolithic visible transmittance ofthe coated glass substrate (10 or 10′) is greater than 0.86 but lessthan 0.92 while the sheet resistance of the flash-treated ITO film isgreater than 10 Ω/square but less than 15 Ω/square (or less than 13Ω/square).

In preferred embodiments, the present method further includes depositingan overcoat film onto the substoichiometric indium tin oxide film. Whenprovided, the overcoat film preferably is sputter deposited to athickness of between 100 Å and 1,300 Å. The overcoat film can be formedof various materials. For example, it can be formed of silicon nitride,silicon oxynitride, silicon dioxide, tin oxide, titanium oxide, ortitanium oxynitride.

In certain embodiments, the overcoat film 100 is formed of an oxidematerial deposited directly onto the indium tin oxide film 20, and theindium tin oxide film is deposited directly onto the first surface (12or 18) of the glass substrate (10 or 10′). (As noted above, the glasssubstrate preferably is soda-lime glass.) In the present embodiments,even though the coating 7 does not have a sodium ion diffusion barrierlayer, the flash-treated indium tin oxide film has a sodiumconcentration of less than 100 ppm, less than 10 ppm, or even less than1 ppm.

Thus, the present invention provides a coated glass substrate having aflash-treated transparent electrically conductive coating. In FIGS. 2and 3, substrate 10′ bears a transparent electrically conductive coating7. In these figures, the coating 7 includes a flash-treated indium tinoxide film 20 and an overcoat film 100. In the embodiment of FIG. 3, thecoating 7 includes, from surface 18 outwardly, an optional base film 15,the flash-treated indium tin oxide film 20, and the overcoat film 100.Films 15, 20, and 100 can be provided in the form of discrete layers,thicknesses of graded film, or a combination of both including at leastone discrete layer and at least one thickness of graded film. While thebase film 15 is shown as a single layer, it can alternatively be aplurality of layers. Preferably, all the films in the coating 7 areoxide, nitride, or oxynitride films. Certain embodiments provide thecoating 7 in the form of multiple layers of different oxide materials(e.g., such that that the coating 7 consists of a plurality of differentoxide films). Preferably, all the films in the coating 7 are sputteredfilms.

The coating 7 preferably is formed of materials, and made by a process(as described above), that allow the coated substrate to have a hazelevel of less than 0.5 or less than 0.3 (e.g., less than 0.2, less than0.1, or even less than 0.09), a roughness R_(a) of less than 3 nm, and amonolithic visible transmittance of greater than 0.82 (preferablygreater than 0.86). It is to be appreciated, however, that theseproperties are optional. For example, higher haze levels may be providedin certain embodiments.

Haze can be measured in well-known fashion, e.g., using a BYK Haze-Gardplus instrument. Reference is made to ASTM D 1003-00: Standard Testmethod for Haze and Luminous Transmittance of Transparent Plastics, thecontents of which are incorporated herein by reference.

In certain embodiments, the coated substrate has a haze of less than 0.3and a surface roughness of less than 3 nm, together with a monolithicvisible transmittance of greater than 0.82 (e.g., after flash treatment)in combination with the flash-treated ITO film having a R_(sheet) ofless than 15 ohms/square, or even less than 13 ohms/square, such asabout 11.5 to 12.5 ohms/square.

As noted above, the coating 7 has low surface roughness. Preferably, theflash-treated coating has a surface roughness R_(a) of less than 3 nm,such as from 1.5 nm to 3.0 nm. The deposition method parameterspreferably are chosen to provide the coating with such a roughness.Alternatively, the coating could be polished or roughened afterdeposition to provide the desired surface roughness. While the flashtreatment may increase the surface roughness by a certain amount (e.g.,0-10%), the final surface roughness preferably is in the ranges notedabove.

The flash treated coated substrate can have particularly good flatness.For example, the coated glass substrate of any embodiment of thisinvention can, even after flash treatment, meet the specifications forallowable annealed glass distortion specified in ASTM 1036-11, theteachings of which are hereby incorporated herein by reference.

When provided, the optional base film 15 can comprise, consistessentially of, or consist of silica, alumina, or a mixture of both. Inother embodiments, the base film 15 comprises titanium dioxide. In stillother embodiments, the base film 15 comprises tin oxide (e.g., SnO₂). Insuch embodiments, the base film 15 may be devoid of indium. For example,a base film 15 consisting of (or at least consisting essentially of) tinoxide is provided in some cases. Compounds of two or more of silica,alumina, titanium dioxide, and tin oxide can be used. Alternatively,other dielectric films may be used. As noted above, the invention alsoprovides embodiments wherein the base film is omitted.

The indium tin oxide film 20 comprises indium tin oxide, optionallytogether with one or more other materials. If desired, zinc, aluminum,antimony, fluorine, carbon nanotubes, or other components can beincluded in the film. Preferably, the indium tin oxide film 20 consistsessentially of (e.g., contains more than 95% by weight), or consists of,indium tin oxide. The indium tin oxide film 20 can contain variousrelative percentages of indium and tin. On a metal-only basis, indium isthe major constituent. That is, indium accounts for more than 50% of thefilm's total metal weight. Preferably, the composition of the film on ametal-only basis ranges from about 75% indium/25% tin to about 95%indium/5% tin, such as about 90% indium/10% tin.

In any embodiment of the present disclosure, the indium tin oxide film20 can optionally be replaced with another type of transparentconductive oxide film. A few well-known examples include fluorinated tinoxide (“FTO”), a doped zinc oxide, such as aluminum-doped zinc oxide(“AZO”), or a doped titanium dioxide, such as niobium-doped TiO₂(“NTO”).

The overcoat film 100 is located over the indium tin oxide film 20. Insome cases, the overcoat film 100 comprises tin oxide. In such cases,the tin oxide-containing overcoat film is devoid of indium oxide. Incertain embodiments, the overcoat film 100 contains at least 75% tin, atleast 85% tin, or at least 95% tin (on a metal-only basis), while alsobeing devoid of indium oxide. For example, the overcoat film 100 mayconsist of (or at least consist essentially of) tin oxide (e.g., SnO₂).Alternatively, the overcoat film can comprise silicon nitride, siliconoxynitride, or both. Further, some embodiments provide the overcoat film100 in the form of an oxide material, such as silicon dioxide.

The coating 7 can optionally include a nitride film between the indiumtin oxide film 20 and the overcoat film 100. When provided, the nitridefilm may comprise one or more of silicon nitride, aluminum nitride, andtitanium nitride. For example, a thin film of silicon nitride canoptionally be positioned directly between (i.e., so as to contact both)the indium tin oxide film and the overcoat film. When provided, thissilicon nitride film (which can optionally include a small amount ofaluminum) may have a thickness of less than 250 Å, or even less than 200Å, e.g., about 150 Å.

In other embodiments, the overcoat film 100 is in contact with theindium tin oxide film 20. Providing the overcoat film 100 directly over(i.e., so as to be in contact with) the underlying indium tin oxide film20 can be advantageous. For example, providing fewer layers andinterfaces may be desirable in connection with optical properties,stress, or both. Moreover, material, energy, and cost can be conservedby providing fewer layers. Also, when the overcoat film 100 comprisestin oxide, while it has a different composition than the indium tinoxide film 20, both contain tin oxide and may thus have particularlygood adhesion to each other.

When provided, the optional base film 15 has a thickness of 50 Å ormore, such as about 70-300 Å. In certain embodiments, the coatingincludes a base film of silica (optionally including some alumina),alumina, titanium dioxide, or tin oxide at a thickness of 75-150 Å. Theinvention also provides embodiments wherein the indium tin oxide film 20is directly on (i.e., in contact with) the substrate surface 18, whichmay be soda-lime float glass.

The coating 7 can optionally further include an oxynitride film locatedon the overcoat film 100. When provided, this oxynitride film can have athickness of between 100 Å and 1,300 Å, such as between 400 Å and 900 Å.The oxynitride film can optionally be directly over (i.e., so as tocontact) the overcoat film 100. The oxynitride film may comprisealuminum, oxygen, and nitrogen. In some cases, the oxynitride film is anexposed outermost film of the coating 7.

In certain embodiments, the optional oxynitride film comprises siliconoxynitride at a thickness of between 400 Å and 900 Å. The siliconoxynitride may, for example, be sputter deposited from one or moresilicon-aluminum targets, such as elemental targets comprising asputterable material consisting of about 83% silicon and 17% aluminum.

Some embodiments of the invention provide a film comprising titaniumoxide 70 over the transparent electrically conductive coating 7.Reference is made to FIG. 4. When provided, the film comprising titaniumoxide 70 preferably is an exposed, outermost film. Thus, when both theoptional oxynitride film and the optional film comprising titanium oxide70 are provided, the film comprising titanium oxide preferably islocated over the oxynitride film. In preferred embodiments, the filmcomprising titanium oxide 70 has a thickness of less than 200 Å, such asfrom 10-75 Å, e.g., about 50 Å.

When provided, the film comprising titanium oxide 70 preferably isphotocatalytic, hydrophilic, or both. Suitable films of this nature aredescribed in U.S. Pat. No. 7,294,404 and Ser. No. 11/129,820 and U.S.Pat. Nos. 7,713,632 and 7,604,865 and Ser. No. 11/293,032 and U.S. Pat.Nos. 7,862,910 and 7,820,309 and 7,820,296, the salient teachings ofeach of which are incorporated herein by reference.

In some embodiments, the coated substrate (10 or 10′) is part of amonolithic glazing. In other embodiments, the coated substrate is partof a multi-pane insulating glazing unit (“IG unit”) 110. Reference ismade to FIGS. 5-9, which depict double-pane IG unit embodiments. It isto be appreciated that the IG unit 110 can alternatively have three ormore panes.

The IG unit 110 preferably includes two glass panes 10, 10′. The twoglass panes 10, 10′ respectively define two opposed external panesurfaces 12, 18. At least one of these two external pane surfaces has aflash-treated transparent conductive oxide coating, such that a desiredone of the two glass panes is a coated glass pane. This coated glasspane is annealed glass having a surface stress of less than 3,500 psi,preferably less than 3,000 psi, such as 2,500 psi or less. Surfacestress can be determined using a grazing angle surface polarimeter asspecified in ASTM C1048 and ASTM C1279, the teachings of which areincorporated herein by reference.

The IG unit 110, while shown as a double-pane unit, can alternatively bea triple-pane unit comprising three glass panes. In such cases, themiddle pane can optionally be heat strengthened or tempered, while oneor both of the two outer panes are annealed. Furthermore, in double-paneIG unit embodiments, the flash-treated coated glass pane can be annealedwhile the other glass pane is heat strengthened or tempered. Or, all theglass panes of any embodiment of the present disclosure can optionallybe annealed.

Some embodiments provide an IG unit that includes at least one annealedglass pane and at least one tempered or heat strengthened glass pane,where the annealed glass pane has a flash-treated transparentelectrically conductive coating 7 while the tempered or heatstrengthened glass pane has its own transparent electrically conductivecoating. In these embodiments, the two transparent electricallyconductive coatings can optionally be different, e.g., they may havedifferent layer stacks, different TCO film thicknesses, or justdifferent TCO film morphologies or characteristics.

In one group of embodiments, the flash-treated transparent electricallyconductive coating 7 is on a #4 surface, a #6 surface, or anotherexternal surface of the inboard pane of an IG unit. By providing thetransparent electrically conductive coating 7 on this surface, thetemperature of the indoor pane under certain conditions can bedecreased. In such cases, by providing a photocatalytic and/orhydrophilic film comprising titanium oxide 70 over the transparentelectrically conductive coating 7, any condensation that may occur onthe room-side surface may be more readily formed into a sheet andevaporated. Reference is made to the embodiment shown in FIG. 6.

The “first” (or “#1”) surface is exposed to an outdoor environment.Accordingly, it is the #1 surface that radiation from the sun firststrikes. The external surface of the outboard pane is the so-calledfirst surface. Moving from the #1 surface toward the interior of thebuilding, the next surface is the “second” (or “#2”) surface. Thus, theinternal surface of the outboard pane is the so-called second surface.Moving further toward the interior of the building, the next surface isthe “third” (or “#3”) surface, followed by the “fourth” (or “#4”)surface. This convention is carried forward for IG units having morethan four major pane surfaces. Thus, for a triple-pane IG unit, the #6surface would be the external surface of the inboard pane.

One group of embodiments provides a triple glazing (e.g., an IG unithaving three panes), and the flash-treated transparent electricallyconductive coating is provided on the #6 surface. In embodiments of thisnature, the #1 and/or #2 surfaces can optionally have other functionalcoatings. The #2 surface, for example, may have a silver-basedlow-emissivity coating, and/or the #1 surface may have anothertransparent electrically conductive coating, an antireflection coating,or a UV-blocking coating. One example is a triple-pane IG unit havingthe flash-treated transparent electrically conductive coating providedon the #6 surface, a triple-silver low-emissivity coating on the #2surface, and a single-silver low-emissivity coating on the #4 surface.

In FIGS. 5-9, substrate 10′ is a transparent glass pane that is part ofan IG unit 110. Commonly, the IG unit 110 has an exterior pane 10 and aninterior pane 10′ separated by at least one between-pane space 800. Aspacer 900 (which can optionally be part of a sash) is provided toseparate the panes 10 and 10′. The spacer 900 can be secured to theinternal surfaces of each pane using an adhesive or seal 700. In somecases, an end sealant 600 is also provided. In the illustratedembodiments, the exterior pane 10 has an external surface 12 (the #1surface) and an internal surface 14 (the #2 surface). The interior pane10′ has an internal surface 16 (the #3 surface) and, in some cases(i.e., when the IG unit is a double-pane unit), an external surface 18(the #4 surface). In other embodiments, the IG unit 110 has three panes,such that the external surface of the inboard pane is the #6 surface.

The IG unit 110 can optionally include a laminated glass panel. In suchcases, the laminated glass panel may be a switchable smart panel or aconventional non-switchable laminated glass panel (i.e., laminated glassthat is not switchable between different optical states).

The IG unit 110 can optionally be mounted in a frame (e.g., a windowsash or frame) such that the external surface 12 of the exterior pane 10is exposed to an outdoor environment 77 while the external surface 18 ofthe interior pane 10′ is exposed to a room-side interior environment.Each internal surface of the IG unit 110 is exposed to a between-panespace 800 of the IG unit. When the IG unit is a triple-pane IG unit, itwill have two between-pane spaces. In some cases, the IG unit 110 is avacuum IG unit.

The IG unit 110 includes at least one flash-treated transparentelectrically conductive coating of the nature described above. In theembodiment of FIG. 5, for example, the external surface 18 of pane 10′has the flash-treated transparent electrically conductive coating 7.Here, the illustrated coating 7 is exposed to an environment (in somecases, a temperature-controlled living space) inside a residentialbuilding or another building.

The IG unit 110 can optionally bear one or more films comprisingtitanium oxide 70, such as a hydrophilic and/or photocatalytic film. Inthe embodiment of FIG. 8, for example, a film comprising titanium oxide70 is provided on the external surface 12 of pane 10, so as to beexposed to an outdoor environment 77 (and thus in periodic contact withrain). The film comprising titanium oxide 70 can be part of aphotocatalytic and/or hydrophilic coating. If desired, the IG unit 110can bear two films comprising titanium oxide, e.g., one such film on theexternal surface 12 of pane 10 and another such film over aflash-treated transparent electrically conductive coating 7 on theexternal surface 18 of pane 10′.

Thus, in some cases, there are two films comprising titanium oxide onthe IG unit. When provided, these two films may be different. Forexample, the external surface of the outboard pane and the externalsurface of the inboard pane can both have photocatalytic films, but theycan be different (e.g., in terms of thickness or composition). Ifdesired, a photocatalytic film on the external surface of the inboardpane can be responsive to activation by indoor light, while aphotocatalytic film on the external surface of the outboard panerequires direct sunlight for activation. More generally, the indoorphotocatalytic film may have a higher level of photoactivity (e.g., itmay be thicker, doped to shift absorption into the visible, and/or itmay have a more highly photoactive composition) than the outdoorphotocatalytic film. When provided, the films comprising titanium oxidemay, of course, be applied over one or more other films. For example, afirst titanium oxide containing film can be provided over aflash-treated transparent electrically conductive coating on theexternal surface 12 of pane 10 while a second titanium oxide containingfilm can be provided over a flash-treated transparent electricallyconductive coating on the external surface 18 of pane 10′.

The IG unit 110 preferably includes one or more low-emissivity coatings80. In the embodiment of FIG. 9, the IG unit 110 includes alow-emissivity coating 80 on the internal surface 14 of pane 10. Whenprovided, the low-emissivity coating 80 preferably includes at least onesilver-inclusive film, which may contain more than 50% silver by weight(e.g., a metallic silver film). If desired, a low-emissivity coating canalternatively be on the internal surface 16 of pane 10′. In someembodiments, the low-emissivity coating includes three or moreinfrared-reflective films (e.g., silver-containing films).Low-emissivity coatings with three or more infrared-reflective films aredescribed in U.S. patent application Ser. No. 11/546,152 and U.S. Pat.Nos. 7,572,511 and 7,572,510 and 7,572,509 and Ser. No. 11/545,211 andU.S. Pat. Nos. 7,342,716 and 7,339,728, the salient teachings of each ofwhich are incorporated herein by reference. In other cases, thelow-emissivity coating can be a “single silver” or “double silver”low-emissivity coating, which are well known to skilled artisans.

If desired, the embodiment of FIG. 6 can have a low-emissivity coatingon surface 14, on surface 16, or both. The same is true of theembodiments of FIGS. 7 and 8. Similarly, the embodiment of FIG. 9 canoptionally have a low-emissivity coating on surface 16, in addition to(or instead of) having the illustrated low-emissivity coating 80 onsurface 14.

While the embodiment of FIG. 5 shows the flash-treated transparentelectrically conductive coating 7 being on the #4 surface, the #1surface of the IG unit 110 can alternatively be provided with aflash-treated transparent electrically conductive coating. In suchcases, there can optionally be a low-emissivity coating on surface 14,on surface 16, or both. Moreover, both external surfaces 12, 18 of theIG unit 110 can optionally have flash-treated transparent electricallyconductive coatings 7, 7′. For example, the IG unit 110 of FIG. 7 has afirst flash-treated transparent electrically conductive coating 7 on the#4 surface, while a second flash-treated transparent electricallyconductive coating 7′ is on the #1 surface. For triple glazed IG units,a first flash-treated transparent electrically conductive coating can beprovided on the #6 surface of the IG unit, while a second flash-treatedtransparent electrically conductive coating is provided on the #1surface of the IG unit. Or, there can simply be a single flash-treatedtransparent electrically conductive coating on the #1 surface.

Thus, it can be appreciated that the flash-treated transparentelectrically conductive coating can be provided on one or more of thefollowing IG unit surfaces: the #1 surface, the #4 surface (for a doubleglazing), and the #6 surface (for a triple glazing). When applied on the#1 surface, the outboard pane will stay warmer and have lesscondensation. When applied on a #4 or #6 surface, the inboard pane willstay cooler and save energy, but it may catch condensation. In suchcases, a hydrophilic and/or photocatalytic coating may be provided overthe flash-treated transparent electrically conductive coating so as toencourage rapid evaporation of any condensation that may occur. Theflash-treated transparent electrically conductive coating may also bebeneficial for a monolithic glazing, a laminated glass glazing, etc.

The flash-treated transparent electrically conductive coating has anumber of beneficial properties. The ensuing discussion reports severalof these properties. In some cases, properties are reported herein for asingle (e.g., monolithic) pane 10′ bearing the flash-treated transparentelectrically conductive coating on one surface 18 (“the present pane”).In other cases, these properties are reported for a double-pane IG unit110 having the flash-treated transparent electrically conductive coatingon the #4 surface 18 and a triple-silver low-emissivity coating on the#2 surface. The triple-silver low-emissivity coating is knowncommercially as the LoE³-366 product from Cardinal CG Company. In suchcases, the reported properties are for a double-pane IG unit whereinboth panes are clear 2.2 mm annealed soda lime float glass with a ½ inchbetween-pane space filled with an insulative gas mix of 90% argon and10% air (“the present IG unit”). Of course, these specifics are by nomeans limiting to the invention. For example, the flash-treatedtransparent electrically conductive coating can alternatively beprovided on the #1 surface of the IG unit, the low-emissivity coatingcan alternatively be on the #3 surface, the low-emissivity coating canalternatively be a single or double silver low-emissivity coating, etc.Absent an express statement to the contrary, the present discussionreports determinations made using the well-known WINDOW 7.1 computerprogram (e.g., calculating center of glass data) under NFRC100-2010conditions.

The flash-treated coating 7 provides low emissivity. The emissivity ofthe coating 7 is less than 0.35, such as from 0.05 to 0.28. In someembodiments, the emissivity is less than 0.22, less than 0.2, or evenless than 0.18, such as about 0.15. In contrast, an uncoated pane ofclear glass would typically have an emissivity of about 0.84.

The term “emissivity” is well known in the present art. This term isused herein in accordance with its well-known meaning to refer to theratio of radiation emitted by a surface to the radiation emitted by ablackbody at the same temperature. Emissivity is a characteristic ofboth absorption and reflectance. It is usually represented by theformula: E=1−Reflectance. The present emissivity values can bedetermined as specified in “Standard Test Method for Emittance ofSpecular Surfaces Using Spectrometric Measurements,” NFRC 301-2010, theentire teachings of which are incorporated herein by reference.

In addition to low emissivity, the U Value of the present IG unit 110 isvery low. As is well known, the U Value of an IG unit is a measure ofthe thermal insulating property of the unit. The smaller the U value,the better the insulating property of the unit. The U Value of thepresent IG unit is less than 0.3 (i.e., center of glass U value),preferably less than 0.25, and perhaps optimally 0.24 or less, such asfrom 0.20-0.23.

The term U Value is well known in the present art. It is used herein inaccordance with its well-known meaning to express the amount of heatthat passes through one unit of area in one unit of time for each unitof temperature difference between a hot side of the IG unit and a coldside of the IG unit. The U Value can be determined in accordance withthe standard specified for U_(winter) in NFRC 100-2014, the teachings ofwhich are incorporated herein by reference.

A tradeoff is sometimes made in low U value coatings whereby the film(s)selected to achieve a low U value have the effect of decreasing thevisible transmittance to a lower level than is desired and/or increasingthe visible reflectance to a higher level than is ideal. As aconsequence, windows bearing these coatings may have unacceptably lowvisible transmission, a somewhat mirror-like appearance, or suboptimalcolor properties.

In combination with the beneficial properties discussed above, theflash-treated coating 7 has good optical properties. As noted above, atradeoff is sometimes made in low U value coatings whereby the filmsselected to achieve a low U value have the effect of restricting thevisible transmission to a level that is lower than ideal.

To the contrary, the present coating 7 provides an exceptionalcombination of these properties. For example, the present IG unit 110(and the present pane 10′, whether monolithic or as part of the IG unit110) has a visible transmittance T_(v) of greater than 0.5 (i.e., avisible transmission of greater than 50%). Preferably, the present IGunit 110 (and the present pane 10′, whether monolithic or insulated)achieves a visible transmittance T_(v) of greater than 0.60 (i.e., avisible transmission of greater than 60%), or greater than 0.62 (i.e., avisible transmission of greater than 62%), such as about 0.63.

Further, if the triple silver low-emissivity coating is replaced with adouble silver low-emissivity coating like the LoE²-270™ or LoE²-272™coatings from Cardinal CG Company, the present IG unit 110 (and thepresent pane 10′, whether monolithic or insulated) can exhibit a visibletransmittance T_(v) of greater than 0.65 (i.e., a visible transmissionof greater than 65%), or even greater than 0.68, such as about0.69-0.70.

Moreover, if the triple silver low-emissivity coating is replaced with asingle silver low-coating like the LoE-180™ coating from Cardinal CGCompany, the present IG unit 110 (and the present pane 10′, whethermonolithic or insulated) can exhibit a visible transmittance T_(v) ofgreater than 0.70 (i.e., a visible transmission of greater than 70%), oreven greater than 0.75, such as about 0.77.

While the desired level of visible transmission can be selected andvaried to accommodate different applications, preferred embodimentsprovide a coated pane 10′ having a post-flash-treatment monolithicvisible transmission of greater than 82%, greater than 85%, or evengreater than 86%, such as greater than 86% but less than 92%.

The term “visible transmission” is well known in the art and is usedherein in accordance with its well-known meaning to refer to thepercentage of all incident visible radiation that is transmitted throughthe IG unit 110. Visible radiation constitutes the wavelength range ofbetween about 380 nm and about 780 nm. Visible transmittance, as well asvisible reflectance, can be determined in accordance with NFRC 300-2014,Standard Test Method for Determining the Solar and Infrared OpticalProperties of Glazing Materials and Fading Resistance of Systems. Thewell-known WINDOW 7.1 computer program can be used in calculating theseand other reported optical properties.

The flash-treated electrically conductive coating 7 can providedesirable reflected color properties in combination with excellentthermal insulating properties. For example, the present IG unit 110 canoptionally exhibit an exterior reflected color characterized by an “a”color coordinate of between −7 and 2 (e.g., between −5 and 1, such asabout −1.9) and a “b” color coordinate of between −9 and 0 (e.g.,between −6 and −1, such as about −3.4).

The present discussion of color properties is reported using thewell-known color coordinates of “a” and “b.” In more detail, thereported color coordinates result from conventional use of thewell-known Hunter Lab Color System (Hunter methods/units, Ill. D65, 10degree observer). The present color properties can be determined asspecified in ASTM Method E 308, the relevant teachings of which areincorporated herein by reference.

In certain embodiments, the foregoing color properties are provided incombination with the sheet resistance, emissivity, U value, and visibletransmission properties reported above. For example, the following chartdepicts preferred combinations of properties in accordance with certainembodiments (the tabulated properties are after flash treatment).

preferred more preferred Sheet resistance less than 15 Ω/square lessthan 13 Ω/square emissivity less than 0.25 less than 0.18 U value lessthan 0.3 less than 0.25 T_(v monolithic) greater than 82% greater than86%

In one embodiment, a multiple-pane insulating glazing unit includes aninternal pane surface bearing a low-emissivity coating that has only onefilm comprising silver. The multiple-pane insulating glazing unitincludes two glass panes and a between-pane space. The two glass panesrespectively define two opposed external pane surfaces. Thelow-emissivity coating is exposed to the between-pane space of the IGunit. The film comprising silver preferably contains at least 50% silverby weight. A desired one of the two external pane surfaces has aflash-treated transparent conductive oxide coating, such that a desiredone of the two glass panes is a coated glass pane. This coated glasspane is annealed glass having a surface stress of less than 3,500 psi.The transparent conductive oxide coating comprises a flash-treatedindium tin oxide film and an overcoat film. The flash-treated indium tinoxide film has a thickness of less than 1,800 Å and is a sputtered filmhaving a surface roughness of less than 3 nm. In the presentembodiments, the flash-treated indium tin oxide film has a sheetresistance of less than 15 ohms/square in combination with the coatedpane having a monolithic visible transmittance of greater than 0.82. Theflash-treated indium tin oxide film has an optical bandgap of 370 nm orshorter and is characterized by a pre-flash optical bandgap of 400 nm orlonger. In the present embodiments, the IG unit has a U value of lessthan 0.25 together with an IGU visible transmission of greater than 75%.In this embodiment, the IG unit preferably exhibits an exteriorreflected color characterized by an “a” color coordinate of between −6and 0 and a “b” color coordinate of between −8 and −1.

In another embodiment, a multiple-pane insulating glazing unit includesan internal pane surface bearing a low-emissivity coating that has onlytwo films comprising silver. The multiple-pane insulating glazing unitincludes two glass panes and a between-pane space. The two glass panesrespectively define two opposed external pane surfaces. Preferably, eachfilm comprising silver contains at least 50% silver by weight. Thelow-emissivity coating is exposed to the between-pane space of the IGunit. The two glass panes respectively define two opposed external panesurfaces. A desired one of the two external pane surfaces has aflash-treated transparent conductive oxide coating, such that a desiredone of the two glass panes is a coated glass pane. This coated glasspane is annealed glass having a surface stress of less than 3,500 psi.The transparent conductive oxide coating comprises a flash-treatedindium tin oxide film and an overcoat film. The flash-treated indium tinoxide film has a thickness of less than 1,800 Å and is a sputtered filmhaving a surface roughness of less than 3 nm. In the presentembodiments, the flash-treated indium tin oxide film has a sheetresistance of less than 15 Ω/square in combination with the desired panehaving a monolithic visible transmittance of greater than 0.82. Theflash-treated indium tin oxide film has an optical bandgap of 370 nm orshorter and is characterized by a pre-flash optical bandgap of 400 nm orlonger. In the present embodiment, the multiple-pane insulating glazingunit has a U value of less than 0.25 together with an IGU visibletransmission of greater than 65%. In this embodiment, the IG unitpreferably exhibits an exterior reflected color characterized by an “a”color coordinate of between −6 and 0 and a “b” color coordinate ofbetween −8 and −1.

In still another embodiment, a multiple-pane insulating glazing unitincludes an internal pane surface bearing a low-emissivity coating thatincludes three films comprising silver. The multiple-pane insulatingglazing unit includes two glass panes and a between-pane space. The twoglass panes respectively define two opposed external pane surfaces.Preferably, each film comprising silver contains at least 50% silver byweight. The low-emissivity coating is exposed to the between-pane spaceof the IG unit. A desired one of the two external pane surfaces has aflash-treated transparent conductive oxide coating, such that a desiredone of the two glass panes is a coated glass pane. This coated glasspane is annealed glass having a surface stress of less than 3,500 psi.The transparent conductive oxide coating comprises a flash-treatedindium tin oxide film and an overcoat film. The flash-treated indium tinoxide film has a thickness of less than 1,800 Å and is a sputtered filmhaving a surface roughness of less than 3 nm. In the presentembodiments, the flash-treated indium tin oxide film has a sheetresistance of less than 15 Ω/square in combination with the coated panehaving a monolithic visible transmittance of greater than 0.82. Theflash-treated indium tin oxide film has an optical bandgap of 370 nm orshorter and is characterized by a pre-flash optical bandgap of 400 nm orlonger. In the present embodiment, the multiple-pane insulating glazingunit has a U value of less than 0.25 together with an IGU visibletransmission of greater than 60%. In this embodiment, the IG unitpreferably exhibits an exterior reflected color characterized by an “a”color coordinate of between −6 and 1 and a “b” color coordinate ofbetween −7 and −1.

In the foregoing three embodiments, the IG unit can be, for example, adouble-pane unit with coating 7 on the #4 surface and the low-emissivitycoating on the #2 surface. The flash-treated coating 7 can consist ofthe following layers: silicon dioxide at about 100 Å/ITO (90% In/10% Sn)at about 1,200-1,400 Å/tin oxide at about 150 Å/SiON at about 900 Å. Thelow-emissivity coating in the first of the foregoing three embodimentscan, for example, be a single-silver low-emissivity coating like thecommercially available LoE-180™ coating from Cardinal CG Company of EdenPrairie, Minn., USA. The low-emissivity coating in the second of theforegoing three embodiments can, for example, be a double-silverlow-emissivity coating like the commercially available LoE²-270™ orLoE²-272™ coatings from Cardinal CG Company. The low-emissivity coatingin the third of the foregoing three embodiments can, for example, be atriple-silver low-emissivity coating like the commercially availableLoE³-366™ coating from Cardinal CG Company.

While some preferred embodiments of the invention have been described,it should be understood that various changes, adaptations andmodifications may be made therein without departing from the spirit ofthe invention and the scope of the appended claims.

What is claimed is:
 1. A multiple-pane insulating glazing unitcomprising two glass panes and a between-pane space, the two glass panesrespectively defining two opposed external pane surfaces, a desired oneof the two external pane surfaces having a flash-treated transparentconductive oxide coating such that a desired one of the two glass panesis a coated glass pane, said coated glass pane being annealed glasshaving a surface stress of less than 3,500 psi, the coating comprising aflash-treated indium tin oxide film and an overcoat film on theflash-treated indium tin oxide film, the flash-treated indium tin oxidefilm having a thickness of less than 1,800 Å, the flash-treated indiumtin oxide film being a sputtered film having a surface roughness of lessthan 3 nm, the flash-treated indium tin oxide film having a sheetresistance of less than 15 Ω/square in combination with said coated panehaving a monolithic visible transmittance of greater than 0.82, theflash-treated indium tin oxide film having an optical bandgap of 370 nmor shorter and being characterized by a pre-flash optical bandgap of 400nm or longer, the multiple-pane insulating glazing unit including aninternal pane surface bearing a low-emissivity coating that has only onefilm comprising silver, the film comprising silver containing at least50% silver by weight, the low-emissivity coating being exposed to thebetween-pane space, the multiple-pane insulating glazing unit having a Uvalue of less than 0.25 together with an IGU visible transmission ofgreater than 75%.
 2. The multiple-pane insulating glazing unit of claim1 wherein the multiple-pane insulating glazing unit exhibits an exteriorreflected color characterized by an “a_(h)” color coordinate of between−6 and 0 and a “b_(h)” color coordinate of between −8 and −1.
 3. Themultiple-pane insulating glazing unit of claim 1 wherein theflash-treated indium tin oxide film has a morphology characterized byUHP flash-treatment at 15-45 kW/cm².
 4. The multiple-pane insulatingglazing unit of claim 1 wherein the flash-treated indium tin oxide filmis characterized by a carrier concentration factor of at least
 5. 5. Themultiple-pane insulating glazing unit of claim 1 wherein theflash-treated indium tin oxide film is characterized by a ΔA of sevenpercent or more.
 6. A multiple-pane insulating glazing unit comprisingtwo glass panes and a between-pane space, the two glass panesrespectively defining two opposed external pane surfaces, a desired oneof the two external pane surfaces having a flash-treated transparentconductive oxide coating such that a desired one of the two glass panesis a coated glass pane, said coated glass pane being annealed glasshaving a surface stress of less than 3,500 psi, the coating comprising aflash-treated indium tin oxide film and an overcoat film on theflash-treated indium tin oxide film, the flash-treated indium tin oxidefilm having a thickness of less than 1,800 Å, the flash-treated indiumtin oxide film being a sputtered film having a surface roughness of lessthan 3 nm, the flash-treated indium tin oxide film having a sheetresistance of less than 15 Ω/square in combination with said desiredpane having a monolithic visible transmittance of greater than 0.82, theflash-treated indium tin oxide film having an optical bandgap of 370 nmor shorter and being characterized by a pre-flash optical bandgap of 400nm or longer, wherein the multiple-pane insulating glazing unit includesan internal pane surface bearing a low-emissivity coating that has onlytwo films comprising silver, each of the two films comprising silvercontaining at least 50% silver by weight, the low-emissivity coatingbeing exposed to the between-pane space, the multiple-pane insulatingglazing unit having a U value of less than 0.25 together with an IGUvisible transmission of greater than 65%.
 7. The multiple-paneinsulating glazing unit of claim 6 wherein the multiple-pane insulatingglazing unit exhibits an exterior reflected color characterized by an“a_(h)” color coordinate of between −6 and 0 and a “b_(h)” colorcoordinate of between −8 and −1.
 8. The multiple-pane insulating glazingunit of claim 6 wherein the flash-treated indium tin oxide film has amorphology characterized by UHP flash-treatment at 15-45 kW/cm².
 9. Themultiple-pane insulating glazing unit of claim 6 wherein theflash-treated indium tin oxide film is characterized by a carrierconcentration factor of at least
 5. 10. The multiple-pane insulatingglazing unit of claim 6 wherein the flash-treated indium tin oxide filmis characterized by a ΔA of seven percent or more.
 11. A multiple-paneinsulating glazing unit comprising two glass panes and a between-panespace, the two glass panes respectively defining two opposed externalpane surfaces, a desired one of the two external pane surfaces having aflash-treated transparent conductive oxide coating such that a desiredone of the two glass panes is a coated glass pane, said coated glasspane being annealed glass having a surface stress of less than 3,500psi, the coating comprising a flash-treated indium tin oxide film and anovercoat film on the flash-treated indium tin oxide film, theflash-treated indium tin oxide film having a thickness of less than1,800 Å, the flash-treated indium tin oxide film being a sputtered filmhaving a surface roughness of less than 3 nm, the flash-treated indiumtin oxide film having a sheet resistance of less than 15 Ω/square incombination with said coated pane having a monolithic visibletransmittance of greater than 0.82, the flash-treated indium tin oxidefilm having an optical bandgap of 370 nm or shorter and beingcharacterized by a pre-flash optical bandgap of 400 nm or longer,wherein the multiple-pane insulating glazing unit includes an internalpane surface bearing a low-emissivity coating that includes three filmscomprising silver, each of the films comprising silver containing atleast 50% silver by weight, the low-emissivity coating being exposed tothe between-pane space, the multiple-pane insulating glazing unit havinga U value of less than 0.25 together with an IGU visible transmission ofgreater than 60%.
 12. The multiple-pane insulating glazing unit of claim11 wherein the multiple-pane insulating glazing unit exhibits anexterior reflected color characterized by an “a_(h)” color coordinate ofbetween −6 and 1 and a “b_(h)” color coordinate of between −7 and −1.13. The multiple-pane insulating glazing unit of claim 11 wherein theflash-treated indium tin oxide film has a morphology characterized byUHP flash-treatment at 15-45 kW/cm².
 14. The multiple-pane insulatingglazing unit of claim 11 wherein the flash-treated indium tin oxide filmis characterized by a carrier concentration factor of at least
 5. 15.The multiple-pane insulating glazing unit of claim 13 wherein theflash-treated indium tin oxide film is characterized by a ΔA of sevenpercent or more.